Entering the break means you are commencing the overhead break maneuver......basically flying down the right side of the ship, executing a sharp break turn, slowing to landing speed and dirtying up into landing configuration. The idea is to go from over the ship (overhead) to being downwind, abeam the LSO platform, in landing configuration and "on-speed" ready to start your approach turn.

"Breaking the deck" refers to being the lowest guy (or flight of jets) in the low holding stack overhead the ship. As soon as the launch is complete, you are timing to depart holding, circle around for the overhead (see above), and be on the ball very shortly after the ship creates a post-launch ready deck. You break the deck because you are at the bottom of the stack, and thus will be the first aircraft to trap at the very beginning of the next recovery. Hope that makes sense.